The anterior pituitary hormones are secreted in pulsatile episodes. Most have prominent 24-hour rhythms, some of which are closely related to the sleep wake cycle and stages of sleep. However, little is known about the metabolic significance of these hormone rhythms, either during normal physiologic functioning or during psychiatric illness. Our past sleep-endocrine studies focused on the rhythmic secretion of anterior pituitary and target organ hormones and indicated some new hormone interrelations, specifically that prolactin as well as luteinizing hormone may influence testosterone secretion in men. This proposal will explore these interrelations further in psychiatric patients with severe endogenous depression, in whom hypothalamic disturbance may be a feature of their illness, and also in normal controls. 24-hour rapid blood sampling studies with sleep stage recordings will be performed on depressed patients before and after treatment and on normal controls. LH, FSH, and prolactin will be manipulated individually and in combination to study their influence on testosterone secretion in depressed and normal men both during the day and at night. Perturbation studies also will be used to assess hypothalamo-pituitary-gonadal function in depressed patients, before and after treatment.